A. Technical Field
The present invention relates to projectile detection, tracking, and source localization, and more particularly to a passive system and method of infrared detection, tracking, and source localization of multiple projectiles (such as for example, bullets, rocket propelled grenades (RPG), and mortars) shot simultaneously in optically cluttered environments.
B. Description of the Related Art
Various systems and methods are known for estimating the trajectory of a projectile, such as a bullet or other supersonic projectile, and for determining sniper positions. Some such systems employ acoustic methods to determine projectile trajectory and source location from the acoustic signature of the shock wave generated by the projectile, i.e. from the acoustic muzzle blast generated when the projectile is fired. Representative examples include U.S. Pat. Nos. 5,241,518; 5,912,862; and 5,930,202. However, complex environments, such as battlefield and urban settings, and noise suppression techniques, often make detection of the muzzle blast unreliable and in some cases near impossible. Other types of shooter localization systems commonly known in the art employ optical methods based on infrared technology. However, these detection systems often rely on the visual observation of muzzle flash, and as such are easily defeated by concealing muzzle flash, such as for example by using a silencer, pillow, etc., or in situations where the shooter is behind a wall or other obstruction. Moreover, these systems based on muzzle flash detection cannot determine the trajectory of the bullet, and are susceptible to optical clutter from complex environments.
In U.S. Pat. No. 5,596,509 a passive bullet detection and tracking method is disclosed that does not rely on muzzle flash detection, but rather uses infrared radiation (IR) detection to detect and track the hot projectile trajectories. IR detection has the advantage that is passive. That is, IR detection devices do not emit radiation, unlike active such as for example disclosed in U.S. Pat. No. 5,796,474 which radiate energy to determine projectile trajectory from range data. Instead, passive IR based systems detect heat or infrared radiation emitted from an object. Thus, because an IR detector does not emit radiation, an object being detected and tracked using an IR detector can not easily determine the source or location of the IR detector.
It is important for bullet detection, tracking and source locating systems to operate with the camera/detector/sensor pointing perpendicular to the bullet's trajectory, i.e. a vantage point of an observer, not a party to the shooting. This enables applications such as: reconnaissance by a UAV over an urban combat zone, or surreptitious surveillance of a firelight. It also allows the range of detection, tracking, and localization to be extended to at least 400 meters.
A need exists for a passive system and method for tracking multiple projectiles simultaneously and locating multiple sniper positions from a vantage point that is substantially orthogonal to the projectile trajectories. Such shooter-localization systems are of great interest to for military application for sniper location and urban combat scenarios. Law enforcement agencies have similar interests.